After your Dad's marriage to your now step-mom, in which you gained a sister. Initially hoping to be on good terms with her, she however was always cold towards you. Recently however in seems like she is teasing you around the house and you've taken the bait. After you meet her on your way to the shower one evening, with her wearing her very tight bike shorts that she always wears. She knows that she got you hooked. The following day while your parents are out of the house, after some teasing passion ensues, her cold demeanor soon warms to your touch.